Cloth simulation is all compressing!
The reason I asked you to remove the solidify modifier was to be sure of what was causing the issue, you can add it in the settings and bake it, but when you add solidify modifier do not increase the thickness to a high amount, I have tested it and it produces the same result if I add it before or after the cloth attribute is added in physics... a thickness of 0.1 to 0.2 should do,..... the plane you used to create your cloth is thin so increase it a little bit in z axis to accommodate some thickness because solidify adds some amount of thickness.